1.1 The characteristics of contemporary processors, input, output and storage devices Components of a computer and their uses 1.1.1 Structure and function of the processor (a) The Arithmetic and Logic Unit; ALU, Control Unit and Registers (Program Counter; PC, Accumulator; ACC, Memory Address Register; MAR, Memory Data Register; MDR, Current Instruction Register; CIR). Buses: data, address and control: how this relates to assembly language programs. (b) The Fetch-Decode-Execute Cycle; including its effects on registers. (c) The factors affecting the performance of the CPU: clock speed, number of cores, cache. (d) The use of pipelining in a processor to improve efficiency. (e) Von Neumann, Harvard and contemporary processor architecture. 1.1.2 Types of processor (a) The differences between and uses of CISC and RISC processors. (b) GPUs and their uses (including those not related to graphics). (c) Multicore and Parallel systems. 1.1.3 Input, output and storage (a) How different input, output and storage devices can be applied to the solution of different problems. (b) The uses of magnetic, flash and optical storage devices. (c) RAM and ROM. (d) Virtual storage.
-Any idea what sort of processor powers your smartphone? What is a processor!? This topic is going to unlock the secrets behind the CPU (what we sometimes call the BRAIN of a Computer) Did you know that 30 years ago, Acorn Computers switched on their first ever processor, the Acorn RISC Machine, or ARM. Now, they power 95% of smartphones & 12 billion ARM chips shipped last year. Professor Steve Furber (University of Manchester) speaks about how he and Sophie Wilson started the project
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A von Neumann processor consists of a single Arithmetic Logic Unit (ALU), a single Control
Unit (CU) and a single Memory Unit (MU).
The ALU is where arithmetic and logical operations are performed and the result stored in a
special register called the Accumulator (ACC).
The CU controls the timing of operations by generating a clock signal. Operations take place
at regular intervals according to this signal.
The MU is where programs are stored when they are ready to run. Each instruction and item
of data in the program will have a memory address associated with it.
All of the components inside the central processing unit (CPU) are connected by the bus
system. The address bus carries memory addresses from the memory unit to registers in the
CPU. The data bus carries data and the control bus carries control signals.
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There are different types of CPU. To increase efficiency, an additional co-processor may
be installed to carry out specific operations (e.g. floating point). Parallel processors use
multiple CPUs to complete more tasks per unit time. Array processors, or vector processors,
all work together on the same task. Multicore processors can support multiple paths of
execution (multithreading). An example would be a modern quad or dual core CPU.
• A Graphics Processing Unit (GPU) is a separate processor on the motherboard or separate
graphics card. Its role is to handle graphics operations and improve user experience. It is
specifically designed to process large amounts of data but on a specific task. A GPU can be
thought of as a vector processor.
• Each CPU has an instruction set that it supports. Modern CPUs tend to have complex
instructions (e.g. an Intel® or AMD® processor). This is Complex Instruction Set Computer
(CISC) architecture. Each instruction may take more than one clock cycle to complete.
• Some CPUs have simpler instructions. This is Reduced Instruction Set Computer (RISC)
architecture. Examples include the ARM® processor in many smartphones and the Raspberry
Pi® computer. Each instruction is simple and takes only one clock cycle to complete.
• CPUs can be programmed in binary (machine code) or a low-level language called
Assembly language. This uses mnemonics to represent the instructions. The instruction
set, and therefore the Assembly language, will differ slightly between CPUs. The CPU will
need to have a program called an assembler to convert the Assembly language code into
Communication between the CPU and devices occurs over buses, which are split into three
main parts, running at different speeds:
1. address bus to specify where the data to be saved/loaded can be found
2. data bus to send the data to be saved or transfer the data to be loaded into the CPU
3. control bus to specify the operation to be performed and for other control signals.
• The CPU is the ‘heart’ of the computer.
• CPUs are measured by clock speed and architecture; for example, a 64-bit processor is more
capable than a 32-bit processor.
• A fast CPU connected to a slow device will be idle most of the time. The slow device, for
example an old hard drive, is known as a ‘bottleneck’, as the data slows down while passing
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• The number of transistors in a CPU has doubled every two years since the 1960s. This is
known as ‘Moore’s law’ (1965).
• All devices that contain a microprocessor have memory to draw data from.
How different input, output and storage devices can be applied to the solution of different problems.
(b) The uses of magnetic, flash and optical storage devices. (c) RAM and ROM. (d) Virtual storage.
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All computer systems have components responsible for input, processing, storage and
• All computing systems are made up of a combination of hardware and software, where
hardware is physical and could be made up of separate parts (e.g. a monitor and mouse),
or be combined in a single unit (e.g. a mobile telephone). Software will make use of the
hardware and perform useful tasks through a series of instructions that are executed by the
microprocessor in the hardware.
• No system functions without systems software that brings hardware and software together.
The two most common types of systems software are the operating system and system
• Programs exist as zeros and ones in random-access memory (RAM), which is structured in
such a way that various tasks could each inhabit a defined memory area, like rooms in a
hotel can host very different people.
• Read-only memory (ROM) is used by all devices for configuration. ROM is usually loaded
before RAM in a boot sequence.
• System start-up software is the other main type of systems software. This is normally found
in the ROM, whereas the operating system is normally found on secondary storage devices,
such as a hard disk. Start-up software has the job of getting the system ready to load up the
main operating system.
• Start-up (or booting) follows a certain procedure for every computer system. Boot loaders
are found on storage devices that have been set up as bootable, so a hard disk might
contain a file with all the settings and preferences saved by a user.
• Before the data is read, computers perform power-on self-test (POST). If a hardware part is
missing, the computer will usually beep or display an error message and refuse to boot.
...vary by function and computer type. A smartphone tends to have
smaller devices for faster interaction with a user, while a company payroll computer will
have a large cheque-reading device that can process thousands of documents with little
user intervention. The most common industrial input devices are optical and magnetic
readers that simplify batch input. In factories, sensors and actuators make robots functional
by giving them the ability to ‘see’ and ‘hear’, as well as move themselves about.
Sensors are becoming more popular as input devices as our computers become more
personal – we carry them in our hands, we wear them on our wrists, we meet other
people with similar devices – there is so much more to sense than in the old days of office
Errors are common with input, so a check digit validation is used to increase reliability of
Touch screen – To allow the user to use a menu based system to pick their beverage.
Chip and pin – To allow the user to pay by credit card.
Actuator – Used to dispense the coffee.
Printer – Used to print a receipt.
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The Little Man Computer (LMC) is an instructional model of a computer, created by Dr. Stuart Madnick in 1965. The LMC is generally used to teach students, because it models a simple von Neumann architecture computer - which has all of the basic features of a modern computer.
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